Radio receiving system



June 9, 1931. E. G. DANn-:LsoN

RADIO RECEIVING SYSTEM Filed June 23 1925 FIE 1 /A mii.

a wn d 9 9 f 4. l. 4 5 1/ 1 n 7 e M 5 l 7 FUE-E N VEN T01? Eemfsr 6.DAN/5.1.50 Mi @d w La A r ron/vus Patented June 9, 1931 une ERNESTG.DANIELSON, F SAN FRNCISCO, CALIFORNIA.

RADIO RECEIVING SYSTEM Application .led J une 23,

This invention relates generally vto electrical systems which employone, or more vacuum tubes or electron relays. It has particularreference to systems of this kind in which the electron relays employmetallic filaments which are energized from a source of current.

It is an object of this invention to devise novel means forautomatically informing an operator when an unsafe potential is beingapplied to the lament of an electron relay.

It is a further object of this invention to devise means for modulatingthe plate circuit of an electron relay with a current of audiblefrequency when a potential o'f excessive value is being applied to thelament of the relay.

Further objects of this invention will appear from the followingdescription in which I have set forth the preferred embodiment of myinvention. It is to be understood that the appended claims are to beaccorded a range of equivalents consistent with the state of the priorart.

Referring to the drawings: Fig. l-is a circuit diagram illustrating aradio receiving circuit embodying my invention.

Figs. 2 and 3 are circuit diagrams illustrating a modification of theinvention shown in Fig. 1.

Fig. 4 is a vertical sectional view of one form of electromagneticvibrator used in connection with said circuits.

It is commonly known that electron relays may be seriously injured byapplying too great a current to the filament. This is particularly trueof relays having filaments which contain rare metals such as thorium,which are vaporized or boiled out if the operating temperature is toogreat. In radio 0 receiving sets, it is common for an inexperiencedoperator to seriously impair the eciency of the vacuum tubes bycarelessly applying an excessive filament potential. Attempts havepreviously been made to protect thelaments by providing means fordisconneet-ing the sup 1y of current when the potential increases a ovea given maximum value. An arrangement of this sort is described in theWireless Ag e of August, 1921, page 25. The diiculty with an arrangementof the sort 1925. Serial No. 38,961.

described in this publication, is that an inexperienced operator willnot understand whether the deenergizration of the relay is caused by toogreat a voltage or by an open circuit in the sup ly of A batterycurrent.. In this invention have provided means for modulating the platecircuit of an electron relay with a current of audible frequencyl whenthe potential across the filament rises above a dangerous value. rIhisaudio frece quency current causes a certain noise in the loud speaker ortelephones which unmistakably indicatesto an'operator that the potentialis too great and that it must be decreased.

One form of my invention as applied to a v standard receiving circuit isshown in Fig. 1

in which the antenn circuit comprises the antennae 1, couplingtransformer 2 and variable capacitance 3 b means of which the antennaecircuit may e tuned to any desired i0 frequency. The grid circuit of athree electrode vacuum tube 4: is connected to the secondary of thetransformer 2 which is shunted by a variable capacitance device 5 fortuningl the grid circuit to the desired frequency. In the grid circuitis located a vgrid condenser 6 shunted by a grid leak resistor 7 forperforming t-he function of keeping the grid at a negative value. Thetube 4 has a grid element 8, a plate element 9 and a filament 10 which80 is heated by an A battery 11 and regulated by a resistance 12. A Bbattery 13 supplies current for the plate circuit. The filament circuitcomprises the A battery 11, conductor 1,4, ilament 10, conductor 15resistance 12 85 back to the battery 11. rIhe circuit described is astandard type which I have selected for purposes of illustrating myinvention, and it is to be understood that I do not limit myself to anyparticular type of circuit as my invent-ion may be embodied in anycircuit using vacuum tubes. y

In carrying out my invention, I connect an electromagnetic vibrator orcircuit interrupter 15 in parallel with the filament l0. 95 In Fig. 1,the winding 16 of the electromagnet 15 is connected at onel end to theconductor 14 by a conductor 17 and its opposite end'to a stationarycontact 18. A. movable contact 19, actuated by the electromagnet 15 isar-4 m0 the grid 8. The rapidly ranged to contact. with contact 18 andcon.- nects with conductor 15 by a conductor 20. As shown in Fig. 4, theelectromagnet- 15 `is provided with a central metallic tube 21 in whichis loosely fitted a steel armature 22 having a stem 23 extending out ofthe tube 21 and engaging a spring 24, preferably of bronze. The spring24 is secured at one end in an insulated base 25 by a screw 26 and atits opposite end carries the contact 19 arranged to cooperate with theContact 18 which is secured to the base 25 by a screw 27. The oppositeend of magnet 15 is also provided with an insulated base 28 to which issecured a guide 29 for a screw 30, which extends into the lower end oftube 21. By means of the screw 30, the limit of travel of the armature22 within the tube 21 may be adjusted. From this it will be seen thatwhen the electromagnet 15 is energized sufficiently to operate, thearmature 22 is raised to separate contacts 18 and 19, thus opening thecircuit of the electromagnet, which thereupon becomes deenergized andthe armature drops, permitting the lcircuit to be closed, due totheaction of spring 24. The cycle is repeated in a well understood manner.

As has been explained above, the electromagnet 15 is connected acrossthe filament 10 or in parallel therewith and is designed to functionwhen the potential drop across the filament exceeds a predeterminedmaximum value. For example where the filament is designed to take avoltage of say 3 volts, the eleetromagnet will function when the voltageexceeds that value.- Thus if the potential drop across the filamentexceeds 3 volts, the electromagnet will rapidly interrupt the circuitbetween contacts 18 and 19 and will effect modulation of the plate oroutput circuit of the vacuum tube. The magnet produces a rapid vibrationof the armature at audible frequency thereby giving a signal that thefilament voltage is excessive. IVhen the voltage is decreased by theoperator to the correct value, the signal is arrested.

In Fig. 2 I have shown the use of means for impressing audible frequencycurrents produced by the interrupter upon the grid circuit or inputcircuit of the electron relay. This is eected by the use of an auxiliarywinding 31 which is connected in series with changing flux in the core15 induces a repeatedly varying current in winding 31 which is repeatedthrough the electron relay 4 and translated by the telephones or othertranslating means.

A further modification of the invention -is shown in Fig. 3 in which theaudible frequen-w cy current is impressed upon the translator byinterrupting the output circuit of the relay. Thus the armature 19 isprovided with an auxiliary contact 33 and is connected to the negativeterminal of the B battery 13. Thus when the arrcature 19 is vibrated theoutput or plate circuit of relay 4 is repeatedly opened' by thetelephones as a loud buzzing noise which is readily distinguishable fromthe radio signals being received.

I claim: t f

1. A radio receiving set including a three electrode vacuum tube and atelephonie device for normally reproducing audible frequencies, meansresponsive to abnormally high voltage on the filament of said tube forinterrupting the filament circuit at audible frequency to protect thefilament and produce a signal of said frequency in the telephoniedevice.

2. In a system of the class described, an electron relay having inputand outputcircuits andan electron emission filament, a source of currentfor energizing said filament, and means drop across the filament above apredetermined4 value for effecting modulation of the input circuit witha current of audio frequency generated by said means.

3. In a radio system of the class described, an electron relay havinginput and output circuits and an electron emission filament, a source ofcurrent for energizing said filament, means responsive to a potentialdrop across the filament above a predetermined -value for eectingmodulation of the input circuit with a current of audio `frequencygenerated by said means, and means in the output circuit for translatinginto sound both signals repeated by the relay and said audio frequencycurrents.

4. In a system of the class described, an electron relay having theusual grid, plate and filament, a circuit for heating said filament, aninput circuit connected with said grid, an output circuit connected withsaid plate, translating means associated with said output circuit, andmeans effective upon an increase in the potential drop across thefilament above a safe value for repeatedly varying the potential uponthe grid at a tone frequency whereby an amplified current is produced inthe output circuit of a tone frequency to actuate said translatingmeans.

5. In a radio receiving system, an electron relay having .input andoutput circuits and a filament adapted to be heated by a current, asource of current connected to said filament, a source of signal energycoupled to the input circuit, means for 'effecting modulation of theoutput circuit with a locally generated source of audio frequencycurrent when the currentvfiowing thru the filament is above a`predetermined maximum value, and means associated with the outputcircuit for translating both signal energy repeated by the relay andsaid audio frequency currents. i

6. In a system of the class described, an

responsive to a potentialelectron relay having input and output circuitsandan electron emission ilament, a source of current for energizin saidfilament, means associated with sald filament and actuated by thepotential drop across the filament above a predetermined value toproduce a continuous audio frequency response in the output circuit.

7. In a system of the class described, an electron relay having inputand output circuits and an electron emission lament, a source of currentfor energizing said lament, means including an electro-magnetic vibratorassociated with vsaid filament and actuated by the potential drop acrossthe lilament above a predetermined value to produce a continuous audiofrequency response in the output circuit.

8.*In a system of the class described, an electron tube relay havinginput and output circuits, an electronV emitting filament, a source ofcurrent for energizing said filament, an electro-magnetic vibrator withan actuating coil connected in parallel with said filament forgenerating a pulsating current of audio frequency and actuated by anincrease in the potential drop across the fila-v ment above a safe valueto generate said current, and an inductance coil in 'series with theinput circuit inductively coupled to said actuating coil for effectingmodulation of the input circuit with said generated current.

9. In a system ofthe class described, an electron tube relay having agrid, plate and filament, a circuit forheatin said filament, an inputcircuit connecting said grid and filament, an output circuit connectingsaid plate and filament, translatin means in said output circuit, andmeans including an electromagnetic vibrator for generating a pulsatingcurrent of audio frequency connected in parallel with the filament andcoupled to the input circuit, said means bein responsive to an increasein the potential rop across the filament above a safe value to modulatethe input circuit with said generated .current whereby an ampliedcurrentof audio frey quency is produced in the output circuit to actuate saidtranslating means.

In testimony whereof, I have hereunto set v m hand.

y ERNEST G. DANIELSON.

